The big problem with any chip amp is getting the heat away from the device. 25/0/25 sounds OK on the face of it but if the speakers are demanding current wise then the 18V may be a safer option. The voltages will be a bit higher anyway when the regulation figure of the tranny is factored in.

There's no right and wrong answer for this one. If you really need the higher voltage swing then use the 25V, if you don't then use the 18V

Cheers Mooly! The speakers are Rega R3's mini floorstanders which are quite easy to drive to a high volume without a lot of power. My main concern is that the amp gets enough voltage to produce a decent bass, I hate soggy bass and one of the reasons I chose this kit was I read it had a nice tight bass. If an 18v transformer will make no difference to a 25v one in this regard, then i'd be as well with the 18v one. I'd value your opinion on this because i'm about to buy the lm3886 kit.

An interesting test! I once tried the Rega's on an Icon Audio valve headphone amp with a 3 wpc speaker output. I was amazed how loud it went but it had no bass power or control. Nice mid and highs though if a little bit veiled.

The transformers i'm looking at are rated for 230v, I get 245v as a norm so I suppose the 2x18v might reach 2x20v at times.

An interesting test! I once tried the Rega's on an Icon Audio valve headphone amp with a 3 wpc speaker output. I was amazed how loud it went but it had no bass power or control. Nice mid and highs though if a little bit veiled.

The transformers i'm looking at are rated for 230v, I get 245v as a norm so I suppose the 2x18v might reach 2x20v at times.

An interesting test! I once tried the Rega's on an Icon Audio valve headphone amp with a 3 wpc speaker output. I was amazed how loud it went but it had no bass power or control. Nice mid and highs though if a little bit veiled.

The transformers i'm looking at are rated for 230v, I get 245v as a norm so I suppose the 2x18v might reach 2x20v at times.

Think i'll go for the 2x18 to be safe.

Yes, the secondary voltage will be higher by that primary voltage percentage difference and you must also add the regulation figure percentage to the secondary voltage as well. That will be in the data sheet and probably around 6%. That's the rise in voltage at light loading.

The chip amp voltage shouldn't really affect the bass as such provided the output isn't near clipping. I would do that test, its a real eye (ear ) opener and you might be surprised at the result.